Do PISA maths and Religion very important go together across countries?

Across 76 countries the link before adjusting for anything is r = -0.73, on a scale from -1 (opposite) to +1 (in step). A version that uses only each country's rank gives -0.78.

Does the link hold within countries over time, not just across countries?

There are not enough years of data within countries to check this over time.

Does PISA maths cause Religion very important?

This analysis cannot answer that. It shows only that the two go together. A link between two country measures, adjusted or not, does not show that either one changes the other. Country figures also say nothing about individual people.

PISA maths vs. Religion very important

Holds up after adjusting for income

A country is not a person. Countries where more people are counted as belonging to this group also tend to differ on the other measure, and that is all. It does not follow that the people in the group are the people with the different score. Making that leap is called the ecological fallacy: reading a pattern across places as a fact about individual people. It is the most common misuse of this kind of data. Religion also varies strongly with region, history and national income, so much of what looks religious here is really those. That is what the adjusted figures are for. The religion shares are estimates for two years only, and the survey questions are asked in rounds that can be ten years apart.

Across 76 countries, PISA maths and Religion very important rise and fall together at r = -0.73 (on a scale from −1 to +1, where 0 means no link). Comparing only countries with similar income (GDP per person) shrinks it to -0.56 (q = 0.032, allowing for the many pairs tested). Much of the first figure is that both measures rise with national income, but a moderate negative link remains.

Comparing countries across the middle half of religion very important, 13.4% to 50.7% of respondents, pisa maths is worse by 54.5 PISA points at the top of that range than the bottom. Comparing only countries with similar national income, the gap is 30.1 PISA points.

Link before adjusting (r)-0.730p = 7.4e-14 · 76 countries

After adjusting for national income-0.560p = 1.8e-7 · likely range [-0.70, -0.38]

p, allowing for regions0.013standard error 0.132 · 5 regions

Check for luck (q)0.032across 12,497 pairs

How to read these.r runs from −1 (one goes up as the other goes down) to +1 (they rise together), and 0 means no link. Adjusting for national income means comparing countries with the same GDP per person, so differences in wealth can’t explain the link. Income is used in percentage terms, since an extra $1,000 means more to a poor country than to a rich one. p is how likely a link this strong would be if there were really none. Below 0.05 means it is unlikely to be chance. Very small values are written in short form: 1.1e-32 means a decimal point followed by 31 zeros and then 11, so very close to zero. The likely range is where the true figure probably lies, and a range that crosses zero means the link could easily be chance. Countries in the same region tend to resemble each other, so the third figure allows for that, which gives a fairer p. The standard error is the typical size of the error in r. Finally, testing this many pairs means some will look strong by luck alone. A q below 0.05 means this link is unlikely to be one of those.

PISA maths · PISA pointslink with income +0.79 · high

Religion very important · % of respondentslink with income -0.66 · high

Both of these rise and fall closely with national income, so a strong link between them before adjusting was close to certain. Read the adjusted figure, not the first one.

“Link with income” is how closely each measure tracks GDP per person across countries, from −1 to +1.

Every country as a dot

best-fit line line after adjusting

Four ways to measure the link

Method	r	p	Countries
Standard (Pearson), not adjusted	-0.730	7.4e-14	76
By rank (Spearman), not adjusted	-0.780	1.0e-16	76
Standard (Pearson), adjusted for national income	-0.560	1.8e-7	76
By rank (Spearman), adjusted for national income	-0.658	1.4e-10	76

The rank version uses only each country’s place in line, from lowest to highest, so a few extreme countries count for less. The adjusted and unadjusted versions use the same 76 countries: those that report both measures and GDP per person. So the gap between them comes from the adjustment, not from a change in which countries are counted. Drop in the size of r after adjusting: +0.170 (a minus sign means it grew).

How solid is it?

Leaving out one country at a time, r ranges from -0.603 (without SGP) to -0.473 (without QAT). The bar above shows that range on a scale from −1 to +1, with the solid line at the full result. The single country that moves r most: QAT (+0.087).

Within each region

Countries are not separate, unrelated cases, and neighbors share a lot. A link that holds inside each region is far more believable than one that shows up only when comparing regions.

	n	r
East Asia & Pacific	13	-0.73
Europe & Central Asia	44	-0.61

By income third

If the link shows up only in the richest third of countries, it is a feature of rich countries, not a general pattern.

	n	r
Poorest third	26	-0.62
Middle third	25	-0.49
Richest third	25	-0.64

By largest religious group

Countries grouped by a label they share, such as main religion, rather than by a number. Groups of fewer than twelve countries are not shown. These groups differ in income, region and history all at once. So a gap between them is a place to start asking questions, not an answer.

	n	r
Christians	49	-0.62
Muslims	15	-0.21

Without outliers (countries far outside the middle half of countries on either measure, by more than one and a half times the width of that middle half): r = -0.560 after dropping 0 countries.

Two series, one country

Both measures over the years for one country you pick. The two charts are stacked so they share only the years along the bottom.

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Over time, within countries

Everything above compares countries with each other at one moment. This section compares each country only with itself over 0years. So a link here can’t come from anything about a country that stays the same, such as its history, geography, institutions or culture.

Not enough history inside each country to look at this over time. That needs countries measured for several years in a row, and at least one of these measures is measured too rarely.

The data

	PISA points	% of respondents	Years
Singapore SGP	575	34%	2022
Macao SAR, China MAC	552	6.63%	2022
Hong Kong SAR, China HKG	540	10.7%	2022
Japan JPN	536	4.58%	2022
Korea, Rep. KOR	527	10.3%	2022
Estonia EST	510	6.54%	2022
Switzerland CHE	508	11.3%	2022
Canada CAN	497	15.5%	2022
Netherlands NLD	493	11.9%	2022
Ireland IRL	492	27.7%	2022, 2010
Belgium BEL	489	13.2%	2022, 2010
Denmark DNK	489	5.73%	2022
United Kingdom GBR	489	15.6%	2022
Poland POL	489	37.3%	2022
Russian Federation RUS	488	17.4%	2018, 2022

OECD databases as named on each indicator: PISA, Social Expenditure Database (SOCX), Income Distribution Database, Development Assistance Committee statistics, Family Database, Government at a Glance, Corporate Tax Statistics, employment and environment statistics
Haerpfer, C. et al., World Values Survey; EVS, European Values Study

Sources

PISA maths

PISA mean mathematics score

OECD · via Our World in Data · CC BY 4.0 (OECD terms and conditions) · updated annual, except the snapshots noted per indicator

The average score of 15-year-olds on the same test in every country taking part. It is scaled so the OECD average in the starting year was 500, with a standard deviation (a typical gap between students) of 100. Held every three years. The 2021 round was held in 2022, and the OECD says it can still be compared with earlier rounds despite the pandemic. The three subjects are treated as measuring the same thing. Their links with each other are above 0.95, and that close match is a fact about the test, not about schooling.

Religion very important

Share saying religion is very important in their life

World Values Survey Association and European Values Study · via Our World in Data · Free for non-commercial use with attribution · updated irregular (survey waves, roughly every 5 years)

The strongest of four answers. The others are "rather", "not very" and "not at all" important. Thinking religion is important is different from attending services, and the gap between them is the interesting part. The United States reports high importance while attendance falls. Several Catholic countries show the reverse. No "better" direction is set, for the same reason as attendance. The survey runs in waves, not every year.

How this was computed

Data used: most recent value in 2010-2025; values come from 2010–2022. To adjust for income, each measure is first predicted from GDP per person (in percentage terms, on a log scale) with a straight-line fit. Only what is left over is then compared. This is called a partial correlation. The line is drawn the standard way (ordinary least squares), which picks the line that comes closest to all the countries at once. The error margins allow for countries in the same region resembling each other, using 5 World Bank regions. The q-value corrects for testing all 12,497 pairs at once, using the Benjamini–Hochberg method. Underlying data last updated DYB 2024. How the country data works · explore PISA maths and Religion very important

This page shows that two measures go together. It does not show that PISA maths changes Religion very important, or the reverse. These figures also describe countries, not individual people. See the ecological fallacy.